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Related to barbiturates: Benzodiazepines




Barbiturates are medicines that act on the central nervous system and cause drowsiness and can control seizures.


Barbiturates are in the group of medicines known as central nervous system depressants (CNS). Also known as sedative-hypnotic drugs, barbiturates make people very relaxed, calm, and sleepy. These drugs are sometimes used to help patients relax before surgery. Some may also be used to control seizures (convulsions). Although barbiturates have been used to treat nervousness and sleep problems, they have generally been replaced by other medicines for these purposes.
These medicines may become habit forming and should not be used to relieve everyday anxiety and tension or to treat sleeplessness over long periods.


Barbiturates are available only with a physician's prescription and are sold in capsule, tablet, liquid, and injectable forms. Some commonly used barbiturates are phenobarbital (Barbita) and secobarbital (Seconal).

Recommended dosage

Recommended dosage depends on the type of barbiturate and other factors such as the patient's age and the condition for which the medicine is being taken. Check with the physician who prescribed the drug or the pharmacist who filled the prescription for the correct dosage.
Always take barbiturates exactly as directed. Never take larger or more frequent doses, and do not take the drug for longer than directed. If the medicine does not seem to be working, even after taking it for several weeks, do not increase the dosage. Instead, check with the physician who prescribed the medicine.
Do not stop taking this medicine suddenly without first checking with the physician who prescribed it. It may be necessary to taper down gradually to reduce the chance of withdrawal symptoms. If it is necessary to stop taking the drug, check with the physician for instructions on how to stop.


See a physician regularly while taking barbiturates. The physician will check to make sure the medicine is working as it should and will note unwanted side effects.
Because barbiturates work on the central nervous system, they may add to the effects of alcohol and other drugs that slow the central nervous system, such as antihistamines, cold medicine, allergy medicine, sleep aids, medicine for seizures, tranquilizers, some pain relievers, and muscle relaxants. They may also add to the effects of anesthetics, including those used for dental procedures. The combined effects of barbiturates and alcohol or other CNS depressants (drugs that slow the central nervous system) can be very dangerous, leading to unconsciousness or even death. Anyone taking barbiturates should not drink alcohol and should check with his or her physician before taking any medicines classified as CNS depressants.

Key terms

Adrenal glands — Two glands located next to the kidneys. The adrenal glands produce the hormones epinephrine and norepinephrine and the corticosteroid (cortisone-like) hormones.
Anemia — A lack of hemoglobin—the compound in blood that carries oxygen from the lungs throughout the body and brings waste carbon dioxide from the cells to the lungs, where it is released.
Central nervous system — The brain and spinal cord.
Hallucination — A false or distorted perception of objects, sounds, or events that seems real. Hallucinations usually result from drugs or mental disorders.
Hypnotic — A medicine that causes sleep.
Porphyria — A disorder in which porphyrins build up in the blood and urine.
Porphyrin — A type of pigment found in living things, such as chlorophyll, that makes plants green and hemoglobin which makes blood red.
Sedative — Medicine that has a calming effect and may be used to treat nervousness or restlessness.
Seizure — A sudden attack, spasm, or convulsion.
Withdrawal symptoms — A group of physical or mental symptoms that may occur when a person suddenly stops using a drug to which he or she has become dependent.
Taking an overdose of barbiturates or combining barbiturates with alcohol or other central nervous system depressants can cause unconsciousness and even death. Anyone who shows signs of an overdose or a reaction to combining barbiturates with alcohol or other drugs should get emergency medical help immediately. Signs include:
  • severe drowsiness
  • breathing problems
  • slurred speech
  • staggering
  • slow heartbeat
  • severe confusion
  • severe weakness
Barbiturates may change the results of certain medical tests. Before having medical tests, anyone taking this medicine should alert the health care professional in charge.
People may feel drowsy, dizzy, lightheaded, or less alert when using these drugs. These effects may even occur the morning after taking a barbiturate at bedtime. Because of these possible effects, anyone who takes these drugs should not drive, use machines or do anything else that might be dangerous until they have found out how the drugs affect them.
Barbiturates may cause physical or mental dependence when taken over long periods. Anyone who shows these signs of dependence should check with his or her physician right away:
  • the need to take larger and larger doses of the medicine to get the same effect
  • a strong desire to keep taking the medicine
  • withdrawal symptoms, such as anxiety, nausea or vomiting, convulsions, trembling, or sleep problems, when the medicine is stopped
Children may be especially sensitive to barbiturates. This may increase the chance of side effects such as unusual excitement.
Older people may also be more sensitive that others to the effects of this medicine. In older people, barbiturates may be more likely to cause confusion, depression, and unusual excitement. These effects are also more likely in people who are very ill.

Special conditions

People with certain medical conditions or who are taking certain other medicines can have problems if they take barbiturates. Before taking these drugs, be sure to let the physician know about any of these conditions:
ALLERGIES. Anyone who has had unusual reactions to barbiturates in the past should let his or her physician know before taking the drugs again. The physician should also be told about any allergies to foods, dyes, preservatives, or other substances.
PREGNANCY. Taking barbiturates during pregnancy increases the chance of birth defects and may cause other problems such as prolonged labor and withdrawal effects in the baby after birth. Pregnant women who must take barbiturates for serious or life-threatening conditions should thoroughly discuss with their physicians the benefits and risks of taking this medicine.
BREASTFEEDING. Barbiturates pass into breast milk and may cause problems such as drowsiness, breathing problems, or slow heartbeat in nursing babies whose mothers take the medicine. Women who are breastfeeding should check with their physicians before using barbiturates.
OTHER MEDICAL CONDITIONS. Before using barbiturates, people with any of these medical problems should make sure their physicians are aware of their conditions:
  • alcohol or drug abuse
  • depression
  • hyperactivity (in children)
  • pain
  • kidney disease
  • liver disease
  • diabetes
  • overactive thyroid
  • underactive adrenal gland
  • chronic lung diseases such as asthma or emphysema
  • severe anemia
  • porphyria
USE OF CERTAIN MEDICINES. Taking barbiturates with certain other drugs may affect the way the drugs work or may increase the chance of side effects.

Side effects

The most common side effects are dizziness, light-headedness, drowsiness, and clumsiness or unsteadiness. These problems usually go away as the body adjusts to the drug and do not require medical treatment unless they persist or interfere with normal activities.
More serious side effects are not common, but may occur. If any of the following side effects occur, check with the physician who prescribed the medicine immediately:
  • fever
  • muscle or joint pain
  • sore throat
  • chest pain or tightness in the chest
  • wheezing
  • skin problems, such as rash, hives, or red, thickened, or scaly skin
  • bleeding sores on the lips
  • sores or painful white spots in the mouth
  • swollen eyelids, face, or lips
In addition, check with a physician as soon as possible if confusion, depression, or unusual excitement occur after taking barbiturates.
Patients who take barbiturates for a long time or at high doses may notice side effects for some time after they stop taking the drug. These effects usually appear within 8-16 hours after the patient stops taking the medicine. Check with a physician if these or other troublesome symptoms occur after stopping treatment with barbiturates:
  • dizziness, lightheadedness or faintness
  • anxiety or restlessness
  • hallucinations
  • vision problems
  • nausea and vomiting
  • seizures (convulsions)
  • muscle twitches or trembling hands
  • weakness
  • sleep problems, nightmares, or increased dreaming
Other side effects may occur. Anyone who has unusual symptoms during or after treatment with barbiturates should get in touch with his or her physician.


Birth control pills may not work properly when taken while barbiturates are being taken. To prevent pregnancy, use additional or additional methods of birth control while taking barbiturates.
Barbiturates may also interact with other medicines. When this happens, the effects of one or both of the drugs may change or the risk of side effects may be greater. Anyone who takes barbiturates should let the physician know all other medicines he or she is taking. Among the drugs that may interact with barbiturates are:
  • Other central nervous system (CNS) depressants such as medicine for allergies, colds, hay fever, and asthma; sedatives; tranquilizers; prescription pain medicine; muscle relaxants; medicine for seizures; sleep aids; barbiturates; and anesthetics.
  • Blood thinners.
  • Adrenocorticoids (cortisone-like medicines).
  • Antiseizure medicines such as valproic acid (Depakote and Depakene), and carbamazepine (Tegretol).
The list above does not include every drug that may interact with barbiturates. Be sure to check with a physician or pharmacist before combining barbiturates with any other prescription or nonprescription (over-the-counter) medicine.



Miller, Norman S. "Sedative-Hypnotics: Pharmacology and Use." Journal of Family Practice 29 (December 1989): 665.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


(băr-bĭt′ū-rāts) (băr-bĭ-tū′rāts)
A group of organic compounds derived from barbituric acid (e.g., amobarbital, phenobarbital, secobarbital) that are used to treat and prevent convulsions, relieve anxiety, or aid sleep. Side effects include drowsiness, depressed respirations, decreased blood pressure, and decreased body temperature. These drugs can also cause tolerance and dependence.
Medical Dictionary, © 2009 Farlex and Partners


Sedative drugs derived from barbituric acid. The barbiturates are classified into three groups according to their duration of action-short, medium and long. Few barbiturates are now widely used, the main exceptions being the very short acting drug thiopentone (thiopental) (Pentothal), which is still used to induce anaesthesia, and the long acting phenobarbitone (phenobarbital) which is used to control some forms of EPILEPSY. The first barbiturate was synthesized from urea in urine provided by a young woman called Barbara, hence the name.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005
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